OK, here it is. What's a moon? Is there only one moon, The Moon. Should the question be "What is a Natural Satellite? Should it be defined based on size, composition, or origin, longevity, parent object?
How big does a moon need to be? Large enough to be detectable is a start, but is it a definition? If there is a size limit, where should it be set?
Is composition important? Can it be its own life bearing world and still be a moon or should it be limited to airless worlds? Should it be similar or dissimilar to the parent planet.
Is the genesis, or origin, of the natural satellite important? Does co-formation make it a moon or a binary planet? Should a moon come from the planet originally or can it be captured? Is capture the only way to get a moon and any other genesis is something else entirely?
Should it be based on longevity? The earth's biggest natural satellite, sometimes called Luna, has been orbiting the earth for a period less than the earth's existence. On the other hand, scientists have detected several small asteroids that orbit the earth in corkscrew orbits for years at a time - Are those objects natural satellites? Are they moons? Are they both?
Should it be based on what it is orbiting? A planet is a natural satellite of a star or stellar remnant. What about natural satellites orbiting Almost Stars, popularly known as brown dwarfs? Some objects orbit the star as primary with periods or influence by a larger mass. Is it a moon if it is co-orbital or does it need to be beholden to the larger mass? Does a moon fall in towards the parent planet or does it move away?
I'm not expressing any preference, yet. What's your definition?